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Chancroid is an STI caused by the short gram-negative bacillus Haemophilus ducreyi. The incubation period is 4–10 days. At the site of inoculation, a vesicopustule develops that breaks down to form a painful, soft ulcer with a necrotic base, surrounding erythema, and undermined edges (eFigure 35–14). There may be multiple lesions due to autoinoculation. The associated lymphadenitis is usually unilateral and consists of tender, matted nodes of moderate size with overlying erythema. These may become fluctuant and rupture spontaneously. With lymph node involvement, fever, chills, and malaise may develop. Patients with cervical infections may have no external signs of infection. The diagnosis is established by culturing a swab of the lesion onto a special medium. In the United States, a probable case of chancroid can be diagnosed if a patient has a consistent ulcer (with or without regional lymphadenopathy) and the alternative, more common diagnoses of syphilis and herpes simplex virus have been ruled out.

eFigure 35–14.

Chancroid. The genital ulcer of chancroid, caused by Hemophilus ducreyi, is deep and painful. It is often accompanied by tender inguinal lymphadenopathy. (Public Health Image Library, CDC)

Chancroid must be differentiated from other genital ulcers. The chancre of syphilis is clean and classically painless, with a hard base and raised borders, whereas the ulcer of chancroid is nonindurated, deep, and painful, with serpiginous borders and often a purulent exudate. Coinfections with other sexually transmitted pathogens (including syphilis, herpes simplex virus, and HIV) are very common, as is super-infection of the chancroid ulcer with other bacteria.

A single dose of either azithromycin, 1 g orally, or ceftriaxone, 250 mg intramuscularly, is effective treatment. Effective multidose regimens are erythromycin base, 500 mg orally three times a day for 7 days, or ciprofloxacin, 500 mg orally twice a day for 3 days.

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Centers for Disease Control and Prevention (CDC). Immigrant, refugee, and migrant health: chancroid. 2017 Apr 6. https://www.cdc.gov/immigrantrefugeehealth/guidelines/domestic/sexually-transmitted-diseases/chancroid.html
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